Field of the Invention
The invention relates to an exercise bicycle, more particularly to an exercise bicycle with an improved transmission system.
Description of the Related Art
Referring to FIG. 1, a conventional bicycle exerciser 10 is shown to comprise a frame 11, a foot pedal assembly 12, a reciprocating arm assembly 13, a resistance wheel 14, and a transmission system 15.
The transmission system 15 includes a first drive shaft 121 mounted rotatably on a rear end portion of the frame 11, and a pair of eccentric arms 122 mounted securely on two ends of the first drive shaft 121 and oriented in opposite directions (only one eccentric arm 122 is shown). The foot pedal assembly 12 includes a pair of foot pedal cranks 123 mounted on a distal end of a respective one of the eccentric arms 122 (see FIG. 2). The reciprocating arm assembly 13 includes a pair of reciprocating arm levers 131 mounted pivotally on a front end portion of the frame 11 on two sides of the latter, and a pair of crank arms 132 (see FIG. 2). Each of the crank arms 132 has a first end connected pivotally to a lower end of a respective one of the arm levers 131 and a second end connected to the distal end of a respective one of the eccentric arms 122. Thus, operation of the foot pedal cranks 123 results in forward and rearward movement of the crank arms 132 to produce reciprocating movement of the arm levers 131.
The resistance wheel 14 is mounted rotatably on the front end portion of the frame 11 between the arm levers 131. The transmission system 15 is used to link the foot pedal cranks 123 to the resistance wheel 14 and further includes a second drive shaft 151, four sprockets 152-155, and two drive chains 156, 157. Referring to FIG. 2, the second drive shaft 151 is mounted rotatably on the frame 11 between the front and rear end portions of the latter. The first sprocket 152 is mounted securely on the first drive shaft 121 between the eccentric arms 122. The second and third sprockets 153, 154 are mounted securely on the second drive shaft 151. The fourth sprocket 155 is mounted securely on an axle 141 of the resistance wheel 14. The first drive chain 156 is trained between the first and second sprockets 152, 153. The second drive chain 157 is trained between the third and fourth sprockets 154, 155.
When the foot pedal cranks 123 are operated, the first drive shaft 121 is rotated to cause reciprocating movement of the arm levers 131 and to rotate the first sprocket 152 therewith. The first sprocket 152 drives the second drive shaft 151 to rotate via the second sprocket 153 and the first drive chain 156, thereby rotating the third sprocket 154. The third sprocket 154 drives the axle 141 to rotate via the fourth sprocket 154 and the second drive chain 157, thereby rotating the resistance wheel 14. When the arm levers 131 are oscillated, the crank arms 132 cause the first drive shaft 121 to rotate, thereby resulting in the rotation of the resistance wheel 14.
It has thus been shown that the conventional bicycle exerciser can be used to exercise the upper and lower parts of the body. The conventional bicycle exerciser shown in FIGS. 1 and 2, however, has the following drawbacks:
1. Note that rotation of the foot pedal cranks 123 occurs when the arm levers 131 are oscillated. Thus, banging of the foot pedal cranks 123 against the legs of the user usually occurs.
2. Smooth operation of the foot pedal assembly 12 is difficult to achieve because the foot pedal cranks 123 are connected eccentrically to the first drive shaft 121.